We prove a version of the Fundamental Theorem of Asset Pricing, which applies to Kabanov's approach to foreign exchange markets under transaction costs. The financial market is modelled by a d x d matrix-valued stochastic process Sigma_t_t=0^T specifying the mutual bid and ask prices between d...

In securities markets, the characterisation of the absence of arbitrage by the existence of state price deflators is generally obtained through the use of the Kreps-Yan theorem. This paper deals with the validity of this theorem in a general framework. We apply this results to the...